Makefile: Revert to PEP 517 mode (#3090)
Makefile: Revert to PEP 517 mode (#3090)

This is a revert of 740b4944439998981701e3782039ffa75da018d3.  It seems
like `--no-use-pep517` breaks too and I can no longer reproduce the
original issue with pip 21.3.1.

Also, adjust the `make clean` target to explicitly remove the ignored
directories too.
edgedb/edgedb,edgedb/edgedb,edgedb/edgedb